DESCRIPTION

Annotates each line in the given file with information from the revision which
last modified the line. Optionally, start annotating from the given revision.

The command can also limit the range of lines annotated.

The report does not tell you anything about lines which have been deleted or
replaced; you need to use a tool such as git diff or the "pickaxe"
interface briefly mentioned in the following paragraph.

Apart from supporting file annotation, git also supports searching the
development history for when a code snippet occurred in a change. This makes it
possible to track when a code snippet was added to a file, moved or copied
between files, and eventually deleted or replaced. It works by searching for
a text string in the diff. A small example:

Walk history forward instead of backward. Instead of showing
the revision in which a line appeared, this shows the last
revision in which a line has existed. This requires a range of
revision like START..END where the path to blame exists in
START.

-p

--porcelain

Show in a format designed for machine consumption.

--incremental

Show the result incrementally in a format designed for
machine consumption.

--encoding=<encoding>

Specifies the encoding used to output author names
and commit summaries. Setting it to none makes blame
output unconverted data. For more information see the
discussion about encoding in the git-log(1)
manual page.

--contents <file>

When <rev> is not specified, the command annotates the
changes starting backwards from the working tree copy.
This flag makes the command pretend as if the working
tree copy has the contents of the named file (specify
- to make the command read from the standard input).

--date <format>

The value is one of the following alternatives:
{relative,local,default,iso,rfc,short}. If --date is not
provided, the value of the blame.date config variable is
used. If the blame.date config variable is also not set, the
iso format is used. For more information, See the discussion
of the --date option at git-log(1).

-M|<num>|

Detect moved or copied lines within a file. When a commit
moves or copies a block of lines (e.g. the original file
has A and then B, and the commit changes it to B and then
A), the traditional blame algorithm notices only half of
the movement and typically blames the lines that were moved
up (i.e. B) to the parent and assigns blame to the lines that
were moved down (i.e. A) to the child commit. With this
option, both groups of lines are blamed on the parent by
running extra passes of inspection.

<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving
within a file for it to associate those lines with the parent
commit.

-C|<num>|

In addition to -M, detect lines moved or copied from other
files that were modified in the same commit. This is
useful when you reorganize your program and move code
around across files. When this option is given twice,
the command additionally looks for copies from other
files in the commit that creates the file. When this
option is given three times, the command additionally
looks for copies from other files in any commit.

<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving
between files for it to associate those lines with the parent
commit.

Include debugging information related to the movement of
lines between files (see -C) and lines moved within a
file (see -M). The first number listed is the score.
This is the number of alphanumeric characters detected
as having been moved between or within files. This must be above
a certain threshold for git blame to consider those lines
of code to have been moved.

-f

--show-name

Show the filename in the original commit. By default
the filename is shown if there is any line that came from a
file with a different name, due to rename detection.

-n

--show-number

Show the line number in the original commit (Default: off).

-s

Suppress the author name and timestamp from the output.

-w

Ignore whitespace when comparing the parent's version and
the child's to find where the lines came from.

THE PORCELAIN FORMAT

In this format, each line is output after a header; the
header at the minimum has the first line which has:

40-byte SHA-1 of the commit the line is attributed to;

the line number of the line in the original file;

the line number of the line in the final file;

on a line that starts a group of lines from a different
commit than the previous one, the number of lines in this
group. On subsequent lines this field is absent.

This header line is followed by the following information
at least once for each commit:

the author name ("author"), email ("author-mail"), time
("author-time"), and timezone ("author-tz"); similarly
for committer.

the filename in the commit that the line is attributed to.

the first line of the commit log message ("summary").

The contents of the actual line is output after the above
header, prefixed by a TAB. This is to allow adding more
header elements later.

SPECIFYING RANGES

Unlike git blame and git annotate in older versions of git, the extent
of the annotation can be limited to both line ranges and revision
ranges. When you are interested in finding the origin for
lines 40-60 for file foo, you can use the -L option like so
(they mean the same thing -- both ask for 21 lines starting at
line 40):

git blame -L 40,60 foo
git blame -L 40,+21 foo

Also you can use a regular expression to specify the line range:

git blame -L '/^sub hello {/,/^}$/' foo

which limits the annotation to the body of the hello subroutine.

When you are not interested in changes older than version
v2.6.18, or changes older than 3 weeks, you can use revision
range specifiers similar to git rev-list:

git blame v2.6.18.. -- foo
git blame --since=3.weeks -- foo

When revision range specifiers are used to limit the annotation,
lines that have not changed since the range boundary (either the
commit v2.6.18 or the most recent commit that is more than 3
weeks old in the above example) are blamed for that range
boundary commit.

A particularly useful way is to see if an added file has lines
created by copy-and-paste from existing files. Sometimes this
indicates that the developer was being sloppy and did not
refactor the code properly. You can first find the commit that
introduced the file with:

git log --diff-filter=A --pretty=short -- foo

and then annotate the change between the commit and its
parents, using commit^! notation:

git blame -C -C -f $commit^! -- foo

INCREMENTAL OUTPUT

When called with --incremental option, the command outputs the
result as it is built. The output generally will talk about
lines touched by more recent commits first (i.e. the lines will
be annotated out of order) and is meant to be used by
interactive viewers.

The output format is similar to the Porcelain format, but it
does not contain the actual lines from the file that is being
annotated.

Each blame entry always starts with a line of:

<40-byte hex sha1> <sourceline> <resultline> <num_lines>

Line numbers count from 1.

The first time that a commit shows up in the stream, it has various
other information about it printed out with a one-word tag at the
beginning of each line describing the extra commit information (author,
email, committer, dates, summary, etc.).

Unlike the Porcelain format, the filename information is always
given and terminates the entry:

"filename" <whitespace-quoted-filename-goes-here>

and thus it is really quite easy to parse for some line- and word-oriented
parser (which should be quite natural for most scripting languages).

Note

For people who do parsing: to make it more robust, just ignore any
lines between the first and last one ("<sha1>" and "filename" lines)
where you do not recognize the tag words (or care about that particular
one) at the beginning of the "extended information" lines. That way, if
there is ever added information (like the commit encoding or extended
commit commentary), a blame viewer will not care.

MAPPING AUTHORS

If the file .mailmap exists at the toplevel of the repository, or at
the location pointed to by the mailmap.file configuration option, it
is used to map author and committer names and email addresses to
canonical real names and email addresses.

In the simple form, each line in the file consists of the canonical
real name of an author, whitespace, and an email address used in the
commit (enclosed by < and >) to map to the name. For example:

Proper Name <commit@email.xx>

The more complex forms are:

<proper@email.xx> <commit@email.xx>

which allows mailmap to replace only the email part of a commit, and:

Proper Name <proper@email.xx> <commit@email.xx>

which allows mailmap to replace both the name and the email of a
commit matching the specified commit email address, and:

Proper Name <proper@email.xx> Commit Name <commit@email.xx>

which allows mailmap to replace both the name and the email of a
commit matching both the specified commit name and email address.

Example 1: Your history contains commits by two authors, Jane
and Joe, whose names appear in the repository under several forms: